LIGHT BEAM DETECTION APPARATUS

A light beam interrupt detection apparatus for use in a vibrating environment comprises a light source for producing a beam of light, a light receiver for receiving and detecting the beam, the receiver having a detector surface sufficiently larger than the beam such that the beam strikes the detector surface as the beam moves during vibrations, and the receiver producing an output signal which is substantially constant when the beam moves over the detector surface without the beam being broken, the output signal to be fed to a signal processor for detecting an interrupt of the beam by an object. The apparatus may be used on a mechanical loom, and the signal processor may detect a variation in the output signal caused by a partial interrupt of the beam, the object being a thread of the loom which is so dimensioned as to block only a part of the beam the thread passes through the beam.